Klyment is offline
Join Date: Aug 2009
Location: Edmonton, Alberta, Canada
I'd keep the A7. I've used the NEX-7, NEX-6, A6000, A7, A7r, A7s, and RX1r and my applications for these cameras sound similar to yours and I have never found anything other than the NEX-7 and the RX1r lacking in terms of AF speed or accuracy. The NEX-7 is even fine in lighting conditions where you'd hand hold at ISO 1600 and below.
With regards to the A7 and Leica M glass, I'm going to assume that you've tried your glass on it before and have noticed that 50mm and wider glass tends to have strong chromatic aberration and corner softness. I don't think that the A7 will give you comparable lenses with these shorter focal lengths. I primarily use my A7 with the 90 Summicron-M E55 pre-ASPH so CA and corner resolution is acceptable and I pair it with the RX1r when needing to shoot digitally.
Website :: Blog
M7 (chrome), IIIf w/ 5cm Summitar, M9 (black), 90 E55 Pre-ASPH 'Cron (chrome), 35mm F/1.4 Nokton SC, 35/2 Biogon (silver), 21mm F/1.8 Ultron, Contax G2 w/ 28, 45, and 90mm
Coolscan 5000, Howtek 4500, ICG 355i
Sigma 18-35/1.8, Angenieux 16-68/2.2, Fujinon 17.5-105/1.8, Speedbooster, BMPCC, Sony F55 // Toyo VX125 (Jade green), 72/5.6 XL, 110/5.6 XL, 210/5.6 Symmar-S. Sony A7R2, 55/1.8, 85/1.8, Sony RX1r // Fotoman 617, 90/8 Super-Angulon // Sony PCM-D100, Zaxcom Nomad-12